HR: 14:55h
AN: T53D-06    [Abstracts]
TI: Deep Structure and Evolution of the Superimposed Tarim Basin, China
AU: * Wang, Q
EM: qcwang@mail.igcas.ac.cn
AB: Most of petroliferous sedimentary basins in China have experienced multiple phases of tectonic evolution and deposition, and are characterized by tectonic and depositional superimposition. The term `superimposed basin' is suggested to describe those basins, which consist of two or more simple prototype basins superimposing vertically and/or coalescing laterally. Seismic tomography images reveal a cluster of anomalies of high P wave velocity, with a total thickness of 250 km, beneath the Tarim basin. Deep sounding survey by converted waves of earthquakes indicates that the Moho is buried to depth of 40 km in the central uplift, and of 50 km in the subsided regions on both sides of the uplift. The basement of the Cenozoic basin undulates in-phase with the Moho without mirror image between the basin basement and the Moho. At the northern margin, the crust and upper mantle of the Tarim basin subducted northward beneath the Tian Shan Mountains, as was revealed by seismic wide-angle reflection/refraction surveys. At the southern margin, an uncoupling structure was revealed by seismic reflection surveys, with a near surface northward thrust from the Kunlun Mountains into the Tarim Basin and a deep subduction of Tibet plateau beneath the Tarim lithosphere. The Tarim Basin is bounded by a strike-slip faults along the Altyn Tagh Mountains, that has an appearance of flower structure in seismic reflection profile. By unroofing the Tertiary and Triassic strata separately, a change from a pre-Triassic uplift to a pre-Tertiary depression is evidenced in the Tarim Basin. It is indicated that the superimposed Tarim Basin underwent at least two tectonic events, one in the early Mesozoic and the other in Cenozoic. The deep structures mentioned above recorded mainly the Cenozoic tectonic event. Since Neogene, northward push of the Tibet plateau has caused a compression structure along the south margin of the Tarim Basin. The lithosphere of the Tarim Basin is pushed passively northward beneath the Tian Shan Mountains. The passive compression results in an arch structure in the Tarim lithosphere. The arch structure is manifested by the central uplift and depressions on its both sides. The Moho depth beneath the depression is 10 km deeper than that beneath the central uplift. Key words: Seismic survey, Tarim Basin, arch structure, lithosphere
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 7200 SEISMOLOGY
DE: 8122 Dynamics: gravity and tectonics
SC: Tectonophysics [T]
MN: Fall Meeting 2005